What is Cornea: Anatomy, Functions, and Treatments

Location and Anatomy of the Cornea

The cornea is the transparent, dome-shaped outermost layer of the eye that covers the iris, pupil, and anterior chamber. It plays a vital role in refracting light to help the eye focus. Anatomically, the cornea consists of five layers:

1. Epithelium – The outermost layer that protects the eye and absorbs oxygen and nutrients.
2. Bowman’s Layer – A tough layer that provides structural support.
3. Stroma – The thickest layer composed of collagen fibers for strength and flexibility.
4. Descemet’s Membrane – A thin but strong inner layer that supports the endothelium.
5. Endothelium – The innermost layer that maintains corneal transparency by controlling fluid levels.

Differences Between Cornea and Retina

The cornea and retina serve distinct roles in vision:

1. Location: The cornea is located at the front of the eye, while the retina is at the back.
2. Function: The cornea focuses incoming light onto the retina, which then converts light into electrical signals for the brain.
3. Structure: The cornea is a transparent, avascular layer, whereas the retina consists of multiple layers of light-sensitive cells and blood vessels.
4. Role in Vision: The cornea provides initial focus, while the retina processes and transmits visual information to the brain.

Corneal Transplant

When the loss of corneal transparency is the cause of visual loss, corneal transplantation is the method of choice of treatment.  When whole thickness of cornea is affected or damaged due to the corneal disease, a full thickness corneal transplantation is done. The damaged cornea of the patient is completely removed and a healthy cornea from a donor’s eye is transplanted.

However, with latest advances, we are able to identify injury restricted to the thinnest layers of the cornea. Remember, the entire cornea itself is only about half a millimeter in thickness.

We can now remove only the damaged layers of the cornea rather than the whole cornea & these treatments have revolutionized the practice of eye transplantation.

Our Chairman, Prof. Dr. Amar Agarwal, has invented one of the most advanced form of corneal transplant called PDEK (Pre Descemet’s endothelial keratoplasty) to treat cases where only the innermost layers of the cornea are replaced and this is done without stitches. Since a very thin tissue is transplanted, the healing time is rapid, the risk of infection and induced astigmatism is extremely low. Plus, graft rejection is very rare. However, it is a very delicate procedure and requires the skills of an expert surgeon.